It is well known that the destruction of metallic and wood articles caused by abrasion, corrosion, heat and fire has a substantial economic impact in many industries. Finding methods for inhibiting these destructive forces are very important. One method uses a protective barrier or coating over the article's exposed surfaces.
There are various types of protective barriers that can be used. One type uses organic compositions, such as paints, varnishes, lacquers, and the like, that are applied directly over the surface of the article. In order to act as a protective barrier, the organic composition must be compatible with the treated surface. Also with some organic compositions, the surface must be pre-treated before application so that proper bonding and adhesion occurs to the surface. For example when applying paints to aluminum or an aluminum alloy surfaces, the surfaces must be thoroughly cleaned and "roughed-up" or "pickled" so that the paint adheres to the surface. When relatively thin paints are used, however, the "roughed-up" or "pickled" underlying surface may be seen through the paint layer which may be undesirable. Also with many organic compositions, the protective barrier formed may be relatively soft and not resistant to abrasions or corrosion. Moreover, the organic compositions themselves often contain flammable ingredients which offer little or no protection against heat and fire.
Another type of protective barrier uses silicate compounds which are chemically bonded to various metallic surfaces. It is widely known, that various silicate compounds can be used to form hard, smooth surfaces that are resistant to abrasion and corrosion. In the lithographic industry, for example, Casson, Jr., et al., (U.S. Pat. No. 3,658,662) discloses lithographic plates made of aluminum or aluminum alloy material, that are silicated to provide a hard, smooth barrier between the plate's surface and the corrosive diazonium salts and other photosensitive coatings used in the lithographic process. Another advantage for using silicate compounds is their heat and fire resistant properties. Kim, (U.S. Pat. No. 4,810,741), for example, discloses an elaborate process for producing a fire-resistant, non-combustible material containing a silicate compound, sodium silicate, and other ingredients that can be used on various combustible materials.
For aluminum articles, there are two general methods used to carry out the silication process: non-electrolytic and electrolytic. With non-electrolytic processes, the aluminum surface is dipped in a silicate containing solution which, reportedly, forms a thin layer of silicate on the aluminum surface. Unfortunately, the layer of aluminum silicate is weakly bonded to the aluminum surface and only partially resistant to acids, bases, or salt water. Also, uniform results are difficult to achieve because variable factors, such as, the impurities on the metal surface, the pH of the solution, the concentration of the silicate, the temperature of the solution, to name a few, can have an impact on the results.
Electrolytic processes, on the other hand, disclosed in Casson. Jr., et al., (U.S. Pat. No. 3,658,662), are more complex and time consuming. Generally, the process uses a basic electrolyte solution of sodium silicate or other salts and aluminum which acts as an anode. Electricity is supplied between the anode and cathode which causes an aluminum silicate barrier to form on the surface of the anode. Although in Casson, Jr., et al, the inventors report that the electrolytic process forms an improved silicated barrier on aluminum, the process can not be used on non-metallic surfaces, such as wood.
A simple process of forming a protective barrier made of silicate-containing material that can be used on both metallic and wood surfaces to provide protection against abrasions, corrosion, heat and fire is highly desirable.